When something seems wrong with the cooling or heating system of a RV, it is difficult to go to the mechanic and simply say something generic like, “my RV is not cooling like it used to.”
A helpful gadget that every RV owner should keep in their unit is an air flow meter. The best one to keep in a RV is one that shows both the air flow coming out of the air conditioner/furnace and tells the temperature. When the air conditioner feels like it is not cooling right, the air flow meter can check the air flow and temperature to help provide specifics like the air not being cool enough or a decrease in air flow. To test, turn on the unit and hold the meter up to the vent of the air conditioner to check air flow. Then switch to temperature and do the same thing.
If you are starting to see a decrease in air flow, chances are it is the cold air return filter. Low air flow coming out of an air conditioning unit may be a sign it is time to change out or clean the filters. To change the filter on a standard AC unit, unscrew the cover from the ceiling of the inside of the unit. You will see two filters inside the cover. Replace or clean these filters, put the unit back together and retest the air flow. You should notice it goes back to running with normal air flow. For ducted roof air units, the filter is generally located behind the cold air return vent.
If the temperature is not what is used to be, it may be time to take the RV to the dealership and have the air conditioner recharged.
It is a good idea to keep an air flow meter handy so you can test the air flow and temperature of your RV’s air conditioning unit and furnace during normal operation. It will allow you to provide a mechanic with more specifics if something is not working properly.